#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
	int a = 0, b = 0;
	double sum1 = 0, sum2 = 0;
	for (a = 1; a <= 99; a += 2)
	{
		sum1 += 1 / a;
	}
	for (b = 2; b <= 100; b += 2)
	{
		sum2 += 1 / b;
	}
	printf("%lf", sum1 - sum2);
	return 0;
}